1. Field of the Invention
The invention relates to an up-drawing continuous casting apparatus and an up-drawing continuous casting method.
2. Description of Related Art
Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A) proposes a free casting method as a groundbreaking up-drawing continuous casting method that does not require a mold. As described in JP 2012-61518 A, a starter is first dipped into the surface of molten metal (i.e., a molten metal surface), and then when the starter is drawn up, molten metal is also drawn up following the starter by surface tension and the surface film of the molten metal. Here, a casting that has a desired sectional shape is able to be continuously cast by drawing up the molten metal through a shape determining member arranged near the molten metal surface, and cooling the drawn up molten metal.
With a normal continuous casting method, the sectional shape and the shape in the longitudinal direction are both determined by a mold. In particular, with a continuous casting method, the solidified metal (i.e., the casting) must pass through the mold, so the cast casting takes on a shape that extends linearly in the longitudinal direction. In contrast, the shape determining member in the free casting method determines only the sectional shape of the casting. The shape in the longitudinal direction is not determined. Therefore, castings of various shapes in the longitudinal direction are able to be obtained by drawing the starter up while moving the starter (or the shape determining member) in a horizontal direction. For example, JP 2012-61518 A describes a hollow casting (i.e., a pipe) formed in a zigzag shape or a helical shape, not a linear shape in the longitudinal direction.
The inventors discovered the problem described below. With the free casting method described in JP 2012-61518 A, molten metal is drawn up through the shape determining member, so a solidification interface is positioned higher than the shape determining member. Therefore, the molten metal is able to be drawn up diagonally instead of vertically, by drawing up the starter while moving the starter (or the shape determining member) in the horizontal direction.                However, if an up-drawing angle θ (i.e., an angle between the molten metal surface and the up-drawing direction; (0°<θ≤90°) is too small, the molten metal that has been drawn up through the shape determining member will end up being offset with respect to the upper surface of the shape determining member, such that the sectional shape of the casting will no longer be able to be controlled. Therefore, a casting in which the up-drawing angle θ of the molten metal is too small was unable to be formed. That is, with the free casting method described in JP 2012-61518 A, the shape in which a casting can be formed may be limited.        